Mauro Iodice INFN Roma (Italy) Hall A Collaboration Meeting - JLAB May 18, 2004

Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004 N. of detected photoelectrons : Cherenkov angle resolutionMinimize Maximize Separation power Particle Particle Particle Particle mass m 2 mass m 1 mass m 2 mass m 1 R ing I maging CH erenkov Fundamentals “ MIP ” Relevant quantities: N P.E. N. of detected photons AND   angular uncertainty  QE = single photoelectron detection efficiency Q = photoconverter Quantum Efficiency T = transmission of radiator, gas and windows

Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004 Freon Radiator: 1800x400x15 mm 3 single box with quartz windows glued on neoceram housing Grid plane: 100  m positive wires (collects electrons ionized in the gap) Wire chamber : composed by 20  m anode wires plane sandwitched between a cathode plane formed by 100  m wires and the cathode plane formed by the photocathodes Three Photocathodes : 403x640 mm 2 each, divided in 8.4 x 8 mm 2 size pads evaporated with a 300 nm CsI layer J LAB Hall A RICH layout – similar to ALICE HMPID RICH

Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004 J LAB Hall A RICH: some components

Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004 J LAB Hall A RICH flying to hunt kaons into the detector hut

Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004 J LAB Hall A RICH Event Display

Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004 J LAB Hall A RICH OPERATING conditions Gas: Pure Methane (Minimize Photon Feedback, High Q.E.) High Voltage: ~ 2100 Volts for a gain of 8x10 4 Grid Voltage: Volts Optimal trigger to read-out delay: ~ 400 ns (peaking time of gassiplex response) MIP charge and hit size cluster charge and hit size

Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004 R ich Performances – key parameters : Angular resolution : N pe  /p ratio : N pe for  and P  Cherenkov angle reconstruction Cherenkov average angle (rad) Nclusters

Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004 Aero Selected  Aero Selected P Aero Selected K (!) Aero Selected K on a large sample of filtered data Separation power Angular resolution  /K population ratio Kaon selection: This would accept ~ pions x  /K ratio 1/100 pion contamination …. But NON GAUSSIAN TAILS GIVE AN IMPORTANT CONTRIBUTION ! R ich Performances – PID :

Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004 R ich – PID Strategy: Particle Identification is also based on the following (correlated) quantities : Single photon  2 distripution (Prob(  2,n dof )) log-likelihood function L For all measured tracks different particle hypothesis ( ,K,P) are made, and the corresponding central Cherenkov angles are computed (  /K/P ) L  /K/P = n Weighted number of reconstructed hits

Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004 R ich – PID – Kaon selection results :  P K Time of coincidence for Aerogel Selected Kaons w/o and w/ rich : AERO KAERO K && RICH K

Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004 R ich – PID – Pion rejection factor : Time of coincidence for Aerogel Selected Pions: effect of Rich Kaon selection N.Evts in the peak Backgnd subtr. =   N.Evts in the peak Backgnd subtr. = 63 Pion rejection ~ 1000 AERO  && RICH K AERO 

Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004 R ich Possible improvements : MWPC stability for high rates For single rates ≤ 60 KHz HV=2100 V is OK In the range 60 KHz – 100 KHz HV=2075 V is OK Above 100 KHz HV must be reduced further  MWPC stability (and mechanics) needs to be studied for high rates running(work is needed!) However running at reduced gain with moderately good performance seems to be feasable (see next slide)  /K separation for p>2.5 GeV/c Doable “just” replacing the radiator. DAQ rate bottleneck (~1KHz) can be overcome replacing front-end

Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004 R ich MWPC performance at lower HV HV = 2100 VHV = 1900 V

Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004 R ich  /K separation for p > 2.5 GeV/c Radiator C6F14 n=1.29  Ch ~ 5mr Radiator C5F12 n=1.24  Ch ~ 5mr 4  separation at ~ 2.5 GeV/c4  separation at ~ 3.0 GeV/c

Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004 C onclusions : The RICH detector has been successfully operated during the hypernuclear experiment It is a powerful tool for Particle Identification Average Cherenkov angle resolution   ~ 5 mr in good agreement with simulations Clean kaon identification is possible with a pion rejection ratio ~1000 Present analysis is still prelminary

Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004 J LAB Hall A RICH flying into the detector hut

Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004 J LAB Hall A RICH Event Display – altri eventi